Foams are gas dispersions in a small amount of a liquid with a broad field of application at the industrial level. In the oil industry, the use of foams has been extended to naturally fractured reservoirs and their main application has been in controlling the advance of gas in exhausted wells close to the gas-oil contact zone, as well as in enhanced recovery processes. In these types of applications, the stability of the foam plays a major role, and it depends on the chemical structure of the surfactant used to generate it, as well as on the existing temperature, pressure and salinity conditions in the reservoir.
The main chemical families of surfactants that have been used to generate foams applied in enhanced recovery processes include: 1) Alkyl-aryl-sulfonates (U.S. Pat. No. 5,273,682), 2) Alkoxy-alkyl-benzene sulfonates (U.S. Pat. No. 5,049,311), 3) Alpha olefin sulfonates (U.S. Pat. No. 4,607,695), 4) Betaines (U.S. Pat. No. 7,104,327) and 5) Alkyl ether sulfates (Department of Energy of the United States of America DE-FC26-03NT15406 Report). However, when the temperature conditions within the reservoirs are elevated (higher than 70° C.), with salinity exceeding 30000 ppm total solids and the concentration of divalent ions, such as calcium and magnesium, is higher than 2000 ppm, the stability of the foam generated by this surfactant chemical families class decreases dramatically.
In order to increase the foams' stability and, hence, their tolerance to high concentrations of divalent ions and/or high temperature, formulations of foaming agents with enhanced properties have been developed, such as the following:
U.S. Pat. No. 3,939,911 describes a three surfactant system applied to enhanced recovery processes in high temperature reservoirs wherein the formation water contains from 200 to 14000 ppm of dissolved polyvalent ions, such as calcium and magnesium. The three surfactant system comprises: 1) Water-soluble salt of an alkyl or alkylaryl sulfonate wherein the alkyl chain may have from 5 to 25 carbon atoms, 2) A phosphate ester surfactant with an average molecular weight not to exceed 1000 AMU and 3) A sulfobetain-based surfactant having the structural formula (2) wherein R is an alkyl group having from 12 to 24 carbon atoms. The combination is stable up to a temperature of at least 107° C. and resistant to bacterial attack and inhibits scale formation.

U.S. Pat. No. 4,703,797 refers to a method for sweep improvement during enhanced oil recovery processes. Said method concerns the generation of foam by the dispersion of the displacing liquid in an aqueous solution containing a surfactant formulation. The surfactant formulation comprises a lignosulfonate-based foaming agent and a surfactant foaming agent. The surfactant foaming agents disclosed include the group consisting of anionic, nonionic and amphoteric surfactants.
U.S. Pat. No. 5,295,540 refers to a foam-based method for improving oil production in subterranean formations comprising: 1) Injecting steam and liquids produced within the formation and 2) Injecting a mixture of steam, a noncondensible gas and an aqueous surfactant-polysaccharide mixture. The disclosed surfactants that may be used include linear toluene sulfonates, alkylaryl sulfonates, dialkykaril sulfonates, alpha olefin sulfonates and dimerized alpha olefin sulfonates.
U.S. Pat. No. 5,542,474 refers to a foam-based method for improving the performance during the steam or carbon dioxide flood in subterranean, crude oil-containing formations comprising at least one production well and one injection well. In the oil recovery process, sweep efficiency through the delivery of steam is improved by: 1) Injecting steam until it starts appearing within the production well and 2) Thereafter, adding a mixture of steam, a noncondensible gas and an aqueous surfactant-polypeptide solution into the formation. The aqueous surfactant-polypeptide solution forms a stable foam with the formation oil at formation conditions. The surfactants used as the base for the foaming agent include sodium and ammonium salts of ethoxylated sulfated alcohols, linear alcohol ethoxylates and linear toluene sulfonates.
The paper “Improving the foam performance for mobility control and improved sweep efficiency in gas flooding” (Ind. Eng. Chem. Res. 2004, 43, 4413-4421) refers that the apparent stability and viscosity of an alpha olefin sulfonates-generated foam in brine with total concentrations of dissolved solids ranging from 30000 to 120000 ppm are substantially improved when formulated with partially hydrolyzed polyacrylamide-based polymers or biopolymers of the xanthan gum type. Moreover, the paper reports that the stability of foams generated by 12-carbon alpha olefin sulfonates is substantially increased when formulated with surfactants of the amine oxide type.
U.S. Pat. No. 7,104,327 provides methods for fracturing high temperature subterranean zones and foamed and viscous aqueous fracturing fluids therefor. The fracturing fluid of said invention comprises water, a terpolymer of 2-acrylamido-2-methylpropane-sulfonic acid, acrylamide and acrylic acid or salts thereof, a gas, a foaming agent and a viscosity breaker for controlling and reducing the viscosity of the fracturing fluid. The foaming agent in said invention is selected from the group consisting of C8-C22 alkylamido-betaine, alpha olefin sulfonate, trimethyl-tallow-ammonium chloride, C8-C22 alkylethoxylate sulfate and trimethyl-coco-ammonium chloride, and coco-amidopropyl betaine is specially mentioned as a foaming agent. Said invention never discloses using alkylamido-betaine and alpha olefin sulfonate mixtures to produce foams, or making use of the synergistic effect of the supramolecular complex thereof, which increases the stability of foams.
The synergistic effect of alkyl amido propyl betaines with anionic surfactants of the alkyl ether sodium sulfate and alkyl sodium sulfate type has been studied in the literature (Langmuir 2000, 16, 1000-1013, Langmuir 2004, 20, 565-571, Langmuir 2004, 20, 5445-5453), mainly indicating the alkyl amido propyl betaines ability to stabilize and enhance the rheological properties (viscosity) of foams generated by said anionic surfactants and that they can be applied in shampoos and hair conditioners. Additionally, the paper “Synergistic sphere-to-rod micelle transition in mixed solutions of sodium dodecyl sulfate and cocoamidopropyl betaine” (Langmuir 2004, 20, 565-571) indicates that the synergistic effect between Cocoamidopropyl betaine and sodium dodecyl sulfate is due to an electrostatic attraction between both surfactants' heads (3).

The patent application U.S. 2007/0142235 A1 protects a composition and process for recovering oil, which consist in injecting an aqueous solution into a subterranean oil-bearing formation through one or more injection wells, displacing the solution into the formation, and recovering the oil from one or more production wells. The aqueous solution contains one or more amphoteric surfactants of the alkyl amido betaines type that form a viscoelastic surfactant gel that is able to reduce the interfacial tension and increase the viscosity of the injection fluid simultaneously in certain oils and brines. Viscoelastic gels are tolerant to electrolytes and multivalent cations, and are particularly useful within reservoirs characterized by medium to high temperatures, high salinity, high concentrations of divalent ions and low porosity. The application refers that the composition for recovering oil comprises one or more amphoteric surfactants selected for their ability to lower the interfacial tension and to increase viscosity simultaneously, an aqueous medium, a secondary surfactant and, optionally, one or more polymers to provide residual viscosity. The patent application indicates that one of the amphoteric surfactants (4), that the secondary surfactant can be selected from the anionic, cationic or non-ionic group, and that the polymer used to provide residual viscosity is selected from the polyacrylamide, partially hydrolyzed polyacrylamide, xanthan gum, hydroxyethyl cellulose or guar gum group. Moreover, the patent application refers that the combination of alkyl amido betaines with secondary surfactants of the linear sodium dodecylbenzene sulfonate and arylalkyl sodium xylene sulfonate type reduces interfacial tension and increases the viscosity of the system. The patent application does not refer using alkyl amido betaines-based amphoteric surfactants and mixtures thereof to generate foams, nor does it disclose using mixtures of alkyl amido betaines and anionic surfactants of the alpha olefin sulfonates type.

On the other hand, supramolecular chemistry is the part of chemistry that deals with the study of systems involving molecules or ions aggregates bound through non-covalent interactions, including electrostatic interactions, hydrogen bonds, π-π interactions, dispersion interactions and solvophobic effects. Supramolecular chemistry can be divided into two large areas: 1) Host-Guest Chemistry and 2) Self-assembly. The difference between these two large areas is a matter of size and form; where there is no significant difference in terms of size and none of the species acts as a host for the other, the non-covalent bond between two or more species is referred to as self-assembly.
From an energetic point of view, supramolecular interactions are much weaker than covalent interactions, which are located within the 150 to 450 Kj/mol energetic range for single bonds. The non-covalent interactions energetic interval ranges from 2 kj/mol for dispersion interactions to up to 300 kj/mol for ion-ion interactions (Table 1), and the sum of several supramolecular interactions can result in highly stable supramolecular complexes.
TABLE 1Strength of Supramolecular InteractionsInteractionStrength (Kj/mol)Ion-ion200-300Ion-dipole 50-200Dipole-dipole 5-50 Hydrogen bond 4-120Cation-π 5-80 π-π 0-50 Van der Walls<5HydrophobicSolvent-solvent interaction energy-related
Computational chemistry is a world-wide extensively used tool for predicting the stability and structure of chemical systems with enhanced potential properties and it has found its application at the industrial level in the development of structure-activity ratio quantitative studies. The computational calculation methods that have been used for this purpose include molecular mechanics methods, quantum methods, including semi-empirical and ab initio methods, as well as the density functional theory methods. As examples in the literature showing the use of computational chemistry for accurately predicting supramolecular interactions in chemical systems and/or chemical processes thermodynamic and kinetic aspects we can quote the papers: 1) Cornucopian Cylindrical Aggregate Morphologies from Self-Assembly of Amphiphilic Triblock Copolymer in Selective Media (Journal of Physical Chemistry B, 2005, 109, 21549-21555), 2) Density Functional Calculations, Synthesis, and Characterization of Two Novel Quadruple Hydrogen-Bonded Supramolecular Complexes (Journal of Physical Chemistry A, 2004, 108, 5258-5267), 3) Strong Decrease of the Benzene-Ammonium Ion Interaction upon Complexation with a Carboxylate Anion (Journal of American Chemical Society, 1999, 121, 2303-2306).
None of said references claims the use of foaming additives applying the synergistic effect of alpha olefin sodium sulfonates and alkyl amido propyl betaines for the development of formulations able to perform in high salinity and temperature environments. This invention presents the advantage of the generated formulations working efficiently in high salinity and temperature environments with high concentrations of calcium and magnesium divalent ions, and, furthermore, the generated foam shows superior stability compared to that generated by the currently used products worldwide.